We introduce the first plasmonic palette utilizing color generation strategies for photorealistic printing with aluminum nanostructures. Our work expands the visible color space through spatially mixing and adjusting the nanoscale spacing of discrete nanostructures. With aluminum as the plasmonic material, we achieved enhanced durability and dramatically reduced materials costs with our nanostructures compared to commonly used plasmonic materials such as gold and silver, as well as size regimes scalable to higher-throughput approaches such as photolithography and nanoimprint lithography. These advances could pave the way toward a new generation of low-cost, high-resolution, plasmonic color printing with direct applications in security tagging, cryptography, and information storage.

Fluorescence imaging is one of the most important research tools in biomedical sciences. However, scattering of light severely impedes imaging of thick biological samples beyond the ballistic regime. Here we directly show focusing and high-resolution fluorescence imaging deep inside biological tissues by digitally time-reversing ultrasound-tagged light with high optical gain (~5×105). We confirm the presence of a time-reversed optical focus along with a diffuse background—a corollary of partial phase conjugation—and develop an approach for dynamic background cancellation. To illustrate the potential of our method, we image complex fluorescent objects and tumour microtissues at an unprecedented depth of 2.5 mm in biological tissues at a lateral resolution of 36 μm×52 μm and an axial resolution of 657 μm. Our results set the stage for a range of deep-tissue imaging applications in biomedical research and medical diagnostics.

Focusing of light in the diffusive regime inside scattering media has long been considered impossible. Recently, this limitation has been overcome with time reversal of ultrasound-encoded light (TRUE), but the resolution of this approach is fundamentally limited by the large number of optical modes within the ultrasound focus. Here, we introduce a new approach, time reversal of variance-encoded light (TROVE), which demixes these spatial modes by variance-encoding to break the resolution barrier imposed by the ultrasound. By encoding individual spatial modes inside the scattering sample with unique variances, we effectively uncouple the system resolution from the size of the ultrasound focus. This enables us to demonstrate optical focusing and imaging with diffuse light at unprecedented, speckle-scale lateral resolution of ~ 5 μm.

Strong field enhancement and confinement in plasmonic nanostructures provide suitable conditions for nonlinear optics in ultracompact dimensions. Despite these enhancements, second-harmonic generation (SHG) is still inefficient due to the centrosymmetric crystal structure of the bulk metals used, e.g., Au and Ag. Taking advantage of symmetry breaking at the metal surface, one could greatly enhance SHG by engineering these metal surfaces in regions where the strong electric fields are localized. Here, we combine top-down lithography and bottom-up self-assembly to lodge single rows of 8 nm diameter Au nanoparticles into trenches in a Au film. The resultant "double gap" structures increase the surface-to-volume ratio of Au colocated with the strong fields in ∼2 nm gaps to fully exploit the surface SHG of Au. Compared to a densely packed arrangement of AuNPs on a smooth Au film, the double gaps enhance SHG emission by 4200-fold to achieve an effective second-order susceptibility χ((2)) of 6.1 pm/V, making it comparable with typical nonlinear crystals. This patterning approach also allows for the scalable fabrication of smooth gold surfaces with sub-5 nm gaps and presents opportunities for optical frequency up-conversion in applications that require extreme miniaturization.

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We report the implementation of a color-capable on-chip lensless microscope system, termed color optofluidic microscope (color OFM), and demonstrate imaging of double stained Caenorhabditis elegans with lacZ gene expression at a light intensity about 10 mW/cm 2 .In the field of modern clinical diagnostics and biological science research, the development of microscopes that are autonomous, compact, low-cost and high-resolution can potentially improve existing microscopy applications and engender new microscope usage. The lensless and fully on-chip microscope systems, termed the optofluidic microscopes (OFM), reported recently can potentially fill this role. 1,2 In brief, the OFM method utilizes microfluidic flow to transport samples across array(s) of small apertures (1 micron or smaller) on a metal-coated CMOS imaging sensor that is illuminated with light. The passage of a sample interrupts light transmission through the apertures, and the time-varying transmission associated with each aperture effectively represents a line trace across the sample. By appropriately compositing these line traces from these apertures, we can then generate a high-resolution image of the sample at a resolution comparable to the aperture size. The diagonal arrangement of the aperture array across the channel floor allows the aperture arrays to fully scan a sample flowing in the channel. Due to this design, sensor pixel size has no impact on the OFM's resolution. 1 In addition, the absence of lenses and other bulk optical elements in the OFM design is particularly advantageous as it allows us to implement highly compact chip-scale microscope systems that are mass-producible in a semiconductor foundry. Finally, as the OFM can directly process samples in fluid media, this method eliminates the need to prepare fluid samples onto a glass slide for standard microscopy examination.The basic OFM design can be altered to provide additional imaging capability. For example, we recently presented a proof-ofconcept for phase imaging in the OFM format based on the use of tightly clustered apertures. 3 In this paper, we present an OFM system that is capable of performing color imaging. This system uses a color CMOS sensor chip in place of a monochromatic CMOS sensor chip in the standard OFM, and employs an aperture array arrangement that accommodates the Bayer color pixel arrangement on such sensors.In the next few paragraphs, we will describe the specifications and operating principle of our color OFM prototype. Next, we will report on the calibration experiments for our prototype and demonstrate that it is capable of determining the concentration of a dye, Trypan Blue, under varying illumination intensity. Finally, we will show color OFM images of the microscopic nematode Caenorhabditis elegans (C. elegans) expressing b-galactosidase with a blue LacZ stain and Ponceau, a nonspecific red stain.The color OFM prototype was fabricated on a color CMOS sensor substrate; the sensor (Aptina, MT9T001P12STC) consists of 2048 Â 1536 pixels of size 3.2 micro...

We have developed a new microscopy design that can achieve wide field-of-view (FOV) imaging and yet possesses resolution that is comparable to a conventional microscope. In our design, the sample is illuminated by a holographically projected light-spot grid. We acquire images by translating the sample across the grid and detecting the transmissions. We have built a prototype system with an FOV of 6 mm × 5 mm and acquisition time of 2:5 s. The resolution is fundamentally limited by the spot size-our demonstrated average FWHM spot diameter was 0:74 μm. We demonstrate the prototype by imaging a U.S. Air Force target and a lily anther. This technology is scalable and represents a cost-effective way to implement wide FOV microscopy systems. © 2010 Optical Society of America OCIS codes: 170.0110, 090.2890, 170.5810.Automated, high-resolution, and cost-effective wide fieldof-view (FOV) microscopy is highly sought for many applications, such as high-throughput screening [1] and whole-slide digital pathology diagnosis [2]. In a conventional microscope, the FOV is inversely related to the microscope objective's resolution due to the critical requirement of aberration correction for the whole viewing area. Commercial products for accomplishing wide FOV imaging typically raster scan the target samples under microscope objectives and reconstitute full-view images from multiple smaller images. This approach requires precise mechanical actuation along two axes. Scaling up the FOV for such an approach requires a linear cost increase (add more objectives) or longer scan time. Recently, exciting in-line holography methods [3,4] demonstrated the potential to cover a wide FOV image very cost effectively and without requiring sophisticated optics and mechanical scanning. In-line holography does require excellent raw data quality, as data noise can significantly distort the computed image and deteriorate resolution. To our knowledge, in-line holography's demonstrated resolution for simple objects is about 1 μm [3]. In this Letter, we report a microscopy technique that employs holography concepts in a different fashion to accomplish wide FOV imaging. Our technique, termed holographic scanning microscopy (HSM), uses a specially written hologram to generate a grid of tightly focused light spots and uses this grid as illumination on the target sample to perform parallel multifocal scanning while the sample is translated across the grid. In comparison to inline holography, the resolution here is fundamentally determined by the focused spot size. Unlike in-line holography, this approach does require mechanical scanning, but the scanning format is a simple one-dimensional (1D) translation. This approach is readily scalable, as we would simply use a large hologram with more projection light spots to accomplish wider FOV imaging.Our HSM prototype demonstration, as shown in Fig. 1(a), used a laser (Excelsior-532-200-CDRH, Spectra Physics, with wavelength of 532 nm and power of 200 mW) as light source. The laser was attenuated, spatial filtered...

Illumination engineering is critical for obtaining high-resolution, high-quality images in microscope settings. In a typical microscope, the condenser lens provides sample illumination that is uniform and free from glare. The associated condenser diaphragm can be manually adjusted to obtain the optimal illumination numerical aperture. In this paper, we report a programmable condenser lens for active illumination control. In our prototype setup, we used a $15 liquid crystal display as a transparent spatial light modulator and placed it at the back focal plane of the condenser lens. By setting different binary patterns on the display, we can actively control the illumination and the spatial coherence of the microscope platform. We demonstrated the use of such a simple scheme for multimodal imaging, including bright-field microscopy, darkfield microscopy, phase-contrast microscopy, polarization microscopy, 3D tomographic imaging, and super-resolution Fourier ptychographic imaging. The reported illumination engineering scheme is cost-effective and compatible with most existing platforms. It enables a turnkey solution with high flexibility for researchers in various communities. From the engineering point-of-view, the reported illumination scheme may also provide new insights for the development of multimodal microscopy and Fourier ptychographic imaging.